/Engine/Source/Editor/UnrealEd/Public/Tools/ToolCompatible.h
Does not currently allow for ArrangeChildren support this might be useful for rendering widgets on top of the tool supporting widget? A general overlay that accepts addtional widgets to render on top of the tool supporting widget might be interesting. For instance, an editable preview graph / editor of the selected widget might work this way (Such as for graph nodes).
template<typename ToolCompatibleWidget> class TToolCompatibleMixin : public ToolCompatibleWidget
TWeakPtr<ITool...
ParentToolkit
Toolkit containing this tool compatible widget.